专业英语焦晓燕(第1次)概要1.ppt

It is one thing to demonstrate that hereditary information resides within replicating molecules of DNA, but quite another to understand what sort of information is stored there. Since the time of Mendel, geneticists had puzzled over this question. Mendelian traits in peas, involving colors and shapes, were the end result of complex processes. What kind of change in the hereditary information would change a Mendelian trait? 证明遗传信息储存在发生复制的DNA分子中是一回事，但理解它是哪种遗传信息是另一回事。自从Mendel时代，遗传学家们对此感到困惑，在Mendel的试验中研究的豌豆的性状，涉及颜色和形状，它们都是DNA经历复杂过程产生的结果。遗传信息的哪种变化导致Mendel研究的豌豆性状的改变呢？ Paragraph 1 The first answer to this question came soon after Mendel’s experiments, but its significance was not readily appreciated. In 1902 a British physician named Archibald Garrod, who was working with one of the early Mendelian genenticists, his countryman William Bateson, noted that certain diseases among his patients were prevalent in particular families. 不久，孟德尔的实验首先回答了这个问题，但是它的重要性并没有得到足够的重识。1902年，英国内科医生Archibald Garrod和早期孟德尔遗传学家的同胞William Bateson工作在一起，注意到在他的病人中某些疾病在特定的家庭中普遍存在。 Paragraph 2 Indeed, if several generations within such families were examined, some of these disorders appeared to be controlled by simple recessive alletes. Garrod concluded that these disorders Mendelian traits that had resulted from past changes in the hereditary information and had been passed down from an ancestor to the affected families. 的确，如果这种疾病在一些家庭中的几代人中出现，那么这种疾病是被简单的隐形等位基因所控制的。Garrod 得出结论，这些疾病是由遗传信息的改变而产生的孟德尔性状，并且它从祖先传给子代，进而感染整个家族。 Garrod proceeded to examine several of these disorders in detail. In one such disorder, alkaptonuria, the patients passed urine that rapidly turned black when exposed to air. Such urine contained homogentisic acid (alkapton ), which air oxidized. Garrod 对这些疾病进行了一系列详细的研究，其中一种黑尿酸症，当这种病人排出的尿暴露到空气中就会迅速变黑。这种尿中含有尿黑酸，在空气中会被氧化。 Paragraph 3 In normal individuals, homogentisic acid is broken down into simpler substances, but the affected patients were unable to carry out that breakdown.